System for Processing a Product During Rotation

The present invention relates to processing systems, and more particularly to control systems for coordinating tool operation with rotor operation.

Systems for processing products such as semiconductor wafers are known and typically include a tool, e.g., a heat lamp, a gas injector, etc., that performs a process on the product while the product is rotated about a central axis. In such systems, the product may be supported on a rotor that is angularly displaced by torque applied to the rotor from a stator. Typically, the tool must perform processing on specific portions of the product, such that a controller which operates the tool must be provided with information on the exact angular position of the product at any particular moment in time. Such information is normally provided to the tool controller from a controller which operates the rotor.

More specifically, the rotor is part of an assembly including at least one and generally a plurality of rotation sensors which each detect features on the rotor and sends this information to the rotor controller. The rotor controller determines the exact rotor position from information provided by the sensors and sends the rotor angular position information to the tool controller as a signal with a time stamp. As such, the tool controller is continuously informed of the angular position of the rotor at any point in time and is able to operate the tool(s) in accordance with this position information. Although a system for coordinating rotor angular position with tool processing of a product has been generally effective, the amount of information sent to the tool controller requires a continuous “polling” process, i.e., a process in which the tool controller requests and receives rotor position data, to determine the rotor angular position as such a process limits the accuracy of tool operation especially at higher rotor speeds.

In one aspect, the present invention is a system for processing a product during rotation, the system comprising a tool configured to perform a process on the product and a rotor assembly including a rotor, the rotor being configured to support the product, and a stator including at least one actuator configured to exert magnetic torque on the rotor so as to angularly displace the rotor about a central axis. A tool controller is configured to operate the tool, to transmit a speed request signal including a desired rotation speed of the rotor and to transmit a control pulse having a threshold value repeating at the expiration of a pulse period, the pulse period being proportional to a desired period of rotation of the rotor at the desired rotation speed of the speed request signal. A rotor controller is configured to receive the speed request signal and the control pulse, to control the at least one actuator of the stator such that the rotor angularly displaces at the desired rotation speed and to transmit a rotor angular position pulse to the tool controller once every predetermined angular displacement of the rotor. The rotor controller is further configured to compare a time when the threshold value of the control pulse is received with a time that the rotor angular position pulse is transmitted and to adjust rotation speed of the rotor when there is a difference between the time the control pulse threshold value is received and the time the rotor angular position pulse is transmitted so as to at least minimize the time difference.

In another aspect, the present invention is again a system for processing a product during rotation comprising a tool configured to perform a process on the product and a rotor assembly including a rotor, the rotor being configured to support the product, and a stator including at least one actuator configured to exert magnetic torque on the rotor so as to angularly displace the rotor about a central axis. A tool controller is configured to operate the tool, to transmit a speed request signal including a desired rotation speed of the rotor, and to transmit a control pulse having a threshold value repeating at the expiration of a pulse period, the pulse period being proportional to a desired period of rotation of the rotor at the desired rotation speed of the speed request signal. A rotor controller is configured to receive the speed request signal, to control the at least one actuator of the stator such that the rotor angularly displaces at the desired rotation speed and to transmit a rotor position pulse and/or rotor phase information to the tool controller once every predetermined angular displacement of the rotor. The rotor controller is further configured to calculate an expected time of position pulse transmission based on the desired speed from the speed request signal, to compare the time the rotor angular position pulse and/or rotor phase information is transmitted to the expected time of position pulse transmission once every predetermined angular displacement of the rotor and to adjust the rotation speed of the rotor when there is a difference between the time the rotor angular position pulse and/or rotor phase information is transmitted and the expected time of position pulse transmission.

1 4 FIGS.- 10 10 12 14 16 18 20 12 12 12 Referring to the drawings in detail, wherein like numbers are used to indicate like elements throughout, there is shown ina systemfor processing a product P during rotation. The product P is preferably a semiconductor wafer, but may be another product or component on which processing is conducted during rotation of the product, such as for example, certain food products, etc. The processing systembasically comprises at least one tool, a rotorprovided by a rotor assembly, a tool controllerand a rotor controller. The toolis configured to perform a process on the product P; with the preferred product P being a semiconductor wafer, the toolmay be a rapid thermal processing device such as a heat lamp for annealing sections of the wafer, an injector for injecting process gas that embeds within the wafer, etc. However, when the product P is an item other than a semiconductor wafer, the toolis configured to perform any other process appropriate for the particular type of product P.

16 14 22 24 14 14 22 24 14 18 12 20 14 20 18 14 C The rotor assemblyincludes the rotor, which is configured to support the product P, and a statorthat includes at least one actuatorconfigured to exert magnetic torque on the rotorso as to angularly displace the rotorabout a central axis A. Preferably, the statorincludes a plurality of the actuatorsspaced circumferentially about the outer perimeter of the rotor, as described in further detail below. The tool controlleris configured to operate the tool, specifically by control signals CS, and to transmit a speed request signal SR to the rotor controllerthat includes a desired rotation speed of the rotor. A new speed request signal SR is sent to the rotor controllereach time the tool controllerrequires a change in rotation speed of the rotorduring tool operation, which typically occurs multiple times during the processing of each product P.

20 24 22 14 20 18 14 14 14 20 18 14 14 14 18 The rotor controlleris configured to receive the speed request signal SR and to control the at least one actuatorof the statorsuch that the rotorangularly displaces at the desired rotation speed. The rotor controlleris also configured to transmit a rotor angular position pulse PP to the tool controlleronce every predetermined angular displacement of the of the rotor, preferably once a revolution so as to be referred to as a top dead center or “TDC” pulse, indicating that a reference point on the rotorhas returned to a starting angular position at the completion of each rotor revolution. However, the angular position pulse PP may be transmitted at any other desired angular displacement of the rotor, such as for example, every one hundred eighty degrees (180°), every one hundred twenty degrees (120°), etc. Further, in addition or as an alternative to the rotor angular position information, the rotor controllermay send a separate digital communication to the tool controller, such as the amount by which the rotorleads or lags a desired angular phase of the rotor, indicating phase accuracy or phase offset of the rotor, so that the tool controlleradjusts tool operation based on this phase information.

18 12 14 18 20 14 18 19 14 18 12 The tool controlleroperates the toolbased on the angular position of the rotoras calculated by the tool controllerusing the rotor angular position pulse PP and/or other rotor phase information from the rotor controller, e.g., the amount of phase lagging or leading from the desired angular position of the rotor. Specifically, the tool controllerincludes a counterhaving a clock, typically provided by a crystal oscillator, that tracks the time between receipt of each angular position pulse PP and/or phase information and is further configured to calculate the angular position of the rotorat any specific instant of time based on a period of time between receipt of the rotor angular position pulse PP/phase information and the specific instant of time. Thereby, the tool controlleris able to operate the toolto process specific portions or locations on the product P.

1 3 4 FIGS.,and 3 FIG. 4 FIG. 18 20 14 20 14 14 C C C C C Referring to, the tool controlleris also configured to transmit a control pulse CP to the rotor controllerin order to command that the rotoris angularly displacing at the desired speed as transmitted to the rotor controllerby the most recently received speed request signal SR. The control pulse CP is a pulse train with a constant period having a threshold value PV, which may be a rising edge, a maximum value/voltage or a falling edge, that repeats at the expiration of a control pulse period p. The control pulse period pis proportional to the period of rotation of the rotorat the desired rotation speed of the most recently transmitted speed request signal SR. Specifically, the period pof the control pulse CP is a rational multiple or a whole fraction of the period of rotation of the rotorat the desired speed or angular velocity. For example, the pulse period pmay be ten times the desired rotation period, as shown in, or the pulse period pmay be one-half the desired rotation period, as depicted in.

3 4 FIGS.and 20 14 14 20 20 14 14 18 E C E E E Referring now to, the rotor controlleris further configured to calculate an expected time of position pulse transmission t, which is based on an anticipated period of the control pulse CP as determined by the rotation speed of the most recent speed request signal SR and prior history of control pulse periods p, and to compare the actual time of transmission of the rotor angular position pulse PP to the expected time of position pulse transmission tonce every predetermined angular displacement of the rotor; preferably once every revolution of the rotor. The expected time of position pulse transmission tis stored within the memory of the rotor controllerand is used by the controllerto ensure that the rotoris rotating at the desired speed of the most recent speed request signal SR. If the rotoris rotating at the desired speed, a rotor angular position pulse PP should be sent to the tool controllerat each expected time of position pulse transmission t.

E E E E 20 14 24 20 20 14 However, if there is a difference between the time that the angular position pulse PP is transmitted and the expected time of position pulse transmission t, the rotor controlleradjusts the rotation speed of the rotor, specifically by adjusting current through the rotor actuatorsas discussed in further detail below. As used herein, each reference to an event occurring “at the same time” includes both events occurring substantially simultaneously and events occurring within a predetermined time interval or time offset and each reference to a “difference” between the timing of two events or events occurring at a “different time” means that the time between the two events is greater than a predetermined time interval/offset. Further, if the rotor controllerreceives the control pulse threshold value PV at a time different than an expected time of position pulse transmission t, i.e., before or after the expected time of position pulse transmission toccurring at the frequency of the threshold value PV, the rotor controlleradjusts the rotation speed of the rotoras necessary and recalculates the expected time of position pulse transmission t.

20 14 20 20 14 Further, the rotor controlleris also configured to compare a time when the threshold value PV of the control pulse CP is received with the most recent time that the angular position pulse PP is transmitted. If the threshold value PV is received at the same time that a position pulse PP is transmitted, the rotoris angularly displacing at the desired speed of the most recent speed request signal SR and no action is taken by the rotor controller. However, if there is a difference between the time the control pulse peak PV is received and the time the most recent position pulse PP is transmitted, the rotor controlleradjusts the rotation speed of the rotor.

10 20 14 18 20 24 14 E Thus, in the present processing system, the rotor controlleradjusts the rotation speed of the rotorin each one of three circumstances: 1) the receipt of a different speed request signal SR from the tool controller; 2) when the position pulse PP is transmitted at a time different than the expected time of position pulse transmission t; and 3) when the threshold value PV of the control pulse CP is received at a time different than the time of transmission of the most recent position pulse PP. In each case, the rotor controlleradjusts electric current through the preferred actuatorsas required to change the actual rotation speed of the rotorto the desired rotation speed and/or at the desired angular phasing, as described in further detail below.

10 12 14 18 20 20 18 18 20 18 10 10 In view of the above, it is clear that the present control systemprovides the benefits of simplified and accurate synchronization of the operation of a toolwith the rotation of a rotor. Such benefits are achieved due to the tool controllersending out a continuous control pulse CP and separate speed request signals SR only when a change in rotor speed is necessary for tool operation, while the rotor controlleronly transmits a position pulse PP at every completion of the predetermined angular displacement, typically once per revolution. Because of the minimization of data both transmitted by the rotor controllerand analyzed by the tool controller, the tool controlleris able to more precisely match tool processing operations with the angular position of the product P, while the rotor controlleris capable of relatively rapidly adjusting rotor rotation speed to the requirements of the tool controller. Also, any latency associated with digital communication of angular phase request and measured phase is eliminated. As a further result and benefit, the processing systemis able to operate at substantially higher rotor rotation speeds and tool processing speeds, thereby decreasing product processing times, increasing product quality, and increasing product production volume. Having described the basic components and operation above, these and other details of the processing systemof the present invention are described in further detail below.

2 FIG. 14 16 30 31 31 32 32 33 33 30 30 34 14 20 34 20 14 30 Referring particularly to, in order to determine the angular position of the rotorso as to generate the once per revolution rotor position pulse PP, the rotor assemblyfurther includes at least one and preferably a plurality of rotation sensors, most preferably three pairsA/B,A/B andA/B of the rotation sensors. Each rotation sensoris configured to sense at least one featureon the rotorand to transmit a signal to the rotor controllerwhen the at least one featureis detected. Then, the rotor controlleris configured to determine the angular position of the rotorbased on all of the signals from the one or more sensors.

14 36 31 31 1 32 32 33 33 30 22 36 30 32 36 20 20 14 14 14 14 30 C C Preferably, the rotorincludes a plurality of radially-outwardly extending teethspaced circumferentially about the central axis A. The preferred three pairsA/B,A/B,A/B of the sensorsare also spaced circumferentially apart about the central axis Aand are mounted on the statorso as to be positioned radially outwardly from the plurality of teeth. Each rotation sensoris configured to detect each one of the teethand to transmit a signal indicating the detection of the one toothto the rotor controller. Based on these sensor signals, the rotor controlleris both able to determine when the rotorhas completed a predetermined angular displacement (e.g., each revolution of the rotor), and then generate the rotor position pulse PP, but is also able to determine the angular position of the rotorat any instant in time and whether the rotoris located at a desired angular position or phase. Further, each rotation sensoris preferably an inductance proximity sensor.

16 30 14 36 30 16 14 10 14 34 16 30 34 14 30 14 32 14 C Although the rotor assemblypreferably has three pairs of sensors, each formed as an inductance proximity sensor, and the rotorpreferably has a plurality of teethdetected by the sensors, the rotor assemblymay have any appropriate arrangement and/or components capable of at least determining when the rotorhas completed each revolution during operation of the system. For example, the rotormay include only a single feature, formed in any appropriate manner, and the rotor assemblymay include only a single sensorthat detects the one featureonce during every revolution of the rotor. Further for example, the sensor(s)may be any other appropriate type of sensor, for example hall effect sensors, optical encoders, magnetic encoders, etc. and the rotormay be provided within any type of feature(s)that are detectable by the particular type of sensor utilized. The scope of the present invention includes all appropriate arrangements for at least detecting or determining each time that the rotorcompletes a predetermined angular displacement about the central axis A, such as for example, one revolution, one hundred eighty degrees, etc.

1 2 FIGS.and 2 FIG. 20 24 14 24 25 26 26 28 26 26 26 26 28 14 36 14 24 Referring now to, the statorpreferably includes a plurality of the actuatorsspaced circumferentially about the perimeter of the rotor. Preferably, each actuatoris a reluctance motor actuatorwhich includes a pair of windings or coil assembliesA,B disposed about a ferromagnetic core, as depicted in. The coil assembliesA,B are connected with a current source (not depicted) such that current flowing through the coil assembliesA,B generates magnetic flux that passes through the coreand both into and out of the rotor, specifically the teeth, to thereby exert torque on the rotor. However, the actuatormay include only a single coil assembly or three or more coil assemblies (neither shown).

24 14 24 14 24 14 C With such motor actuatorsacting in coordination with levitation actuators and radial position actuators (neither shown), the rotoris angularly displaced in a contactless manner that eliminates the need for mechanical roller bearings, bushings, seals or other components which may produce contaminants. However, the at least one actuatormay be any other appropriate device capable of angularly displacing the rotorabout the central axis A. For example, the actuatormay be provided by a single DC motor, an AC motor, etc. having an output shaft that mechanically drives rotation of the rotor, either directly or through an appropriate transmission device (no alternative structures shown).

20 24 20 25 20 26 26 20 26 26 24 20 24 In any case, the rotor controlleris configured to adjust the operation of the one or more actuatorswhenever the controllerdetermines the need to adjust rotor speed. With the preferred motor actuators, the rotor controlleradjusts electric current through the pair of coil assembliesA,B, i.e., by adjusting the output of the current source, in order to adjust the rotor speed. More specifically, the rotor controllerincreases current flow through the coil assembliesA,B to increase rotor speed and conversely decreases current flow, or inverts the phase of current flow, to decrease rotor speed. With other types of actuators, the rotor controlleradjusts the operation of the actuatorsin an appropriate manner to accordingly vary the rotor speed as required.

1 FIG. 10 50 50 12 52 50 12 50 10 50 52 18 52 Referring particularly to, the processing systemmay further comprise one or more secondary toolseach configured to perform a process on the productdifferent than the processing conducted by the primary tooland at least one secondary controllerconfigured to operate the secondary tool. For example, the “primary” toolmay include one or more heat lamps which perform an annealing operation on the product P and the one or more secondary toolsmay be a gas injector, a laser, or any other tool for processing a rotating product P. When the processing systemincludes a secondary tooland a secondary tool controller, the “primary” tool controlleris further configured to transmit the control pulse CP to each secondary controllerto ensure that all processing being conducted on the product P is properly coordinated.

Representative, non-limiting examples of the present invention were described above in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention.

Moreover, combinations of features and steps disclosed in the above detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Furthermore, various features of the above-described representative examples, as well as the various independent and dependent claims below, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings.

All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter. The invention is not restricted to the above-described embodiments, and may be varied within the scope of the following claims.